System for producing a fully impregnated thermoplastic prepreg

ABSTRACT

Fiber-containing polymethyl methacrylate (PMMA) prepregs are described that include a first and second plurality of fibers. The second plurality of fibers is made from a different material than the first plurality of fibers. The PMMA prepregs also contain a polymerized resin that includes polymethyl methacrylate that has been formed from a reactive resin composition that includes methyl methacrylate. Methods of making fiber-containing PMMA prepregs are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.14/880,307 filed Oct. 10, 2015, which is a continuation-in-part of U.S.patent application Ser. No. 14/845,007 filed Sep. 3, 2015, and titled“SYSTEM FOR PRODUCTING A FULLY IMPREGNATED THERMOPLASTIC PREPREG.” Thisapplication is also related to U.S. patent application Ser. No.14/088,034 filed Nov. 22, 2013, and titled “FIBER-CONTAINING PREPREGSAND METHODS AND SYSTEMS OF MAKING,” and to U.S. patent application Ser.No. 14/794,634 filed Jul. 8, 2015, and titled “SYSTEM FOR PRODUCING AFULLY IMPREGNATED THERMOPLASTIC PREPREG.” The entire disclosures of allthese applications are hereby incorporated by reference, for allpurposes, as if fully set forth herein.

BACKGROUND

The use of fiber-reinforced composites is growing in popularity withapplications in transportation, consumer goods, wind energy, andinfrastructure. Some of the many reasons for choosing composites overtraditional materials such as metals, wood, or non-reinforced plasticsinclude reduced weight, corrosion resistance, and improved mechanicalstrength. Within the field of fiber-reinforced polymeric composites,thermoplastics are increasingly being used in place of thermosets as thematrix resin due to better durability, recyclability, thermoformability,improved throughput, lower material cost, and lower manufacturing cost.

Many continuous fiber reinforced thermoplastic composites are producedfrom impregnated tapes. These impregnated tapes may be unidirectionalfiber tapes that are impregnated with a thermoplastic resin. These canbe layered and thermoformed to produce a wide variety of composites ofthe desired shape and strength. There are significant challengesassociated with producing impregnated tapes at low cost and highquality. Traditionally thermoplastic resins are melted and applied tofibers, but molten thermoplastic resins have very high viscosity and,when combined with the high fiber content that is desired, results inincomplete resin impregnation and/or low throughput. What is desired isa continuous manufacturing process with high throughput that producesfully impregnated thermoplastic prepregs without defects and goodcoupling between the fibers and the matrix resin. For the conventionalpartially impregnated thermoplastic prepregs, high pressure is needed inthe consolidation step to promote additional impregnation, whichintroduces excessive flow of the resin matrix and causes detrimentalchanges in fiber orientation in the finished parts. The fullyimpregnated thermoplastic prepregs of the instant invention areadvantageous in achieving the desired properties in final compositeparts, as no additional impregnation is needed in the consolidationstep.

BRIEF SUMMARY

The embodiments described herein provide fully impregnated thermoplasticprepreg products, and specifically systems and methods for making thesame. According to one aspect, a system for manufacturing a fullyimpregnated polymethyl methacrylate prepreg in a continuous processincludes a mechanism for moving a fabric or mat from a starting point toan ending point where the fabric or mat is subjected to a plurality ofprocesses. The fabric or mat is in substantially constant movementbetween the starting point and ending point. The system also includes aresin application mechanism that is configured to apply a methylmethacrylate (MMA) resin to the fabric or mat as the fabric or mat ismoved past the resin application mechanism. The MMA resin is in contactwith an initiator upon application of the MMA resin to the fabric ormat. The initiator facilitates in polymerizing the MMA resin to formpolymethyl methacrylate (PMMA). The system further includes a pressmechanism that is configured to press the MMA resin through the fabricor mat as the fabric or mat is moved past or through the press mechanismsuch that the MMA resin fully saturates the fabric or mat duringpolymerization of the MMA resin. The system additionally includes acuring oven having a temperature of between 40 degrees Celsius and 100degrees Celsius, and more commonly between 60 degrees Celsius and 80degrees Celsius. The curing oven is configured to effect polymerizationof the MMA resin to form PMMA as the fabric or mat is moved through thecuring oven such that the fabric or mat is fully impregnated with athermoplastic PMMA polymer upon exiting the curing oven. The system isconfigured to maintain the MMA resin at a temperature of between 40° C.and 80° C. prior to the application of the MMA resin to the fabric ormat.

According to another aspect, a system for manufacturing a polymethylmethacrylate prepreg includes a mechanism for continuously moving afabric or mat and a resin application component that applies a methylmethacrylate (MMA) resin to the fabric or mat as the fabric or mat iscontinuously moved past the resin application component. The system alsoincludes a press mechanism that presses the fabric or mat during thecontinuous movement of the fabric or mat and subsequent to applicationof the MMA resin to ensure that the MMA resin fully saturates the fabricor mat. The system further includes a curing oven through which thefabric or mat is continuously moved. The curing oven is maintained at atemperature of between 40° C. and 100° C., and more commonly between 60°C. and 80° C., to polymerize the MMA resin and thereby form athermoplastic polymethyl methacrylate (PMMA) polymer so that uponexiting the curing oven, the fabric or mat is fully impregnated with thethermoplastic PMMA polymer.

According to another embodiment, a method of forming a fully impregnatedpolymethyl methacrylate prepreg includes moving a fabric or mat from astarting point to an ending point. The fabric or mat is subjected to aplurality of processes during movement of the fabric or mat between thestarting point and ending point. The fabric or mat is also insubstantially constant movement between the starting point and endingpoint. The method also includes mixing methyl methacrylate (MMA) resinwith an initiator to form an MMA resin mixture. The initiatorfacilitates in polymerizing the MMA resin to form polymethylmethacrylate (PMMA). The method further includes applying the MMA resinmixture to the fabric or mat. The method additionally includes passingthe MMA resin mixture coated fabric or mat through a calendar or pressto press the MMA resin mixture entirely through the fabric or mat suchthat the MMA resin mixture fully saturates the fabric or mat. The methodadditionally includes passing the MMA resin mixture coated fabric or matthrough a curing oven having a temperature that is maintained at between40° C. and 100° C., and more commonly between 60° C. and 80° C., topolymerize the MMA resin and thereby form PMMA. Upon exiting the curingoven, the fabric or mat is fully impregnated with PMMA. Greater than95%, 98%, or even 99% of the MMA resin may be polymerized to form PMMA.

According to another aspect, a method of forming a fully impregnatedpolymethyl methacrylate prepreg product includes applying a methylmethacrylate (MMA) resin to a fabric or mat. The MMA resin is combinedwith an initiator that facilitates in polymerizing the MMA resin to formpolymethyl methacrylate (PMMA). The method also includes passing the MMAresin coated fabric or mat through a calendar or press to fully saturatethe fabric or mat with the MMA resin. The method further includespassing the MMA resin saturated fabric or mat through a curing oven topolymerize the MMA resin throughout the fabric or mat and thereby formthe fully impregnated PMMA prepreg. The fabric or mat is constantlymoved during the above process and the above process occurs in a time ofless than 10 minutes.

According to still another aspect, fiber-containing polymethylmethacrylate prepregs are described that include a first plurality offibers, and a second plurality of fibers that are made from a differentmaterial than the first plurality of fibers. The PMMA prepregs alsoinclude a polymerized resin containing PMMA, where the polymerized resinis formed from a reactive resin composition that includes methylmethacrylate (MMA). The fiber-containing PMMA prepregs may be used infiber-reinforced composite articles that are made at least in part fromthe PMMA prepregs.

In some examples, at least one of the first plurality of fibers and/orthe second plurality of fibers may include reactive fibers that have areactive agent present on the surface of the reactive fibers. Thereactive agent may include (i) a silane coupling moiety, and (ii) areactive acrylate or methacrylate moiety. In further examples, the firstplurality of fibers and the second plurality of fibers may be formedinto a fiber mat, or one or more layers of fiber mat. In additionalexamples, the first plurality of fibers may be formed into a first fibermat, and the second plurality of fibers may be formed into a secondfiber mat. Examples further include prepregs formed from layers of thefirst fiber mat and the second fiber mat stacked on top of each other.

The first plurality of fibers and the second plurality of fibers may beselected from glass fibers, inorganic fibers, carbon fibers, metalfibers, organic fibers, and mineral fibers, among other types of fibers.As noted above, the first and second plurality of fibers are made fromdifferent materials. For example, the first plurality of fibers may beglass fibers and the second plurality of fibers may be carbon fibers.

As noted above, the reactive resin composition used to form thepolymerized PMMA resin composition may include methyl methacrylate (MMA)monomers. Examples of the reactive resin composition also include aninitiator for initiating the polymerization of the MMA monomers.Specific examples of the initiator include an organic peroxide.

According to yet another aspect, a method of making a PMMA prepregincludes forming a stack of fiber mats in contact with a reactive resincomposition that includes methyl methacrylate. The stack of fiber matsmay include layers of a first fiber mat and a second fiber mat stackedon top of each other. The first fiber mat includes a first plurality offibers, and the second fiber mat includes a second plurality of fibersmade from a different material than the first plurality of fibers. Forexample, the first plurality of fibers may include glass fibers, and thesecond plurality of fibers may include carbon fibers. The method furtherincludes curing the reactive resin composition in the one or more layersof the fiber mat to form the fiber-containing PMMA prepreg. For example,the reactive resin composition and the stack of fiber mats may be heatedto a polymerization temperature for the resin. In additional examples,the reactive resin composition in the stack of fiber mats may be pressedand heated to cure the reactive resin composition.

According to yet still another aspect, a method of making a PMMA prepregincludes forming one or more layers of fiber mat in contact with areactive resin composition comprising methyl methacrylate. The one ormore layers of fiber mat include a first plurality of fibers, and asecond plurality of fibers made of a different material than the firstplurality of fibers. For example, the first plurality of fibers mayinclude glass fibers, and the second plurality of fibers may includecarbon fibers. The method further includes curing the reactive resincomposition in the one or more layers of the fiber mat to form thefiber-containing PMMA prepreg. For example, the reactive resincomposition in the one or more layers of the fiber mat may be heated toa polymerization temperature for the resin. In additional examples, thereactive resin composition in the one or more layers of the fiber matmay be pressed and heated to cure the reactive resin composition.

BRIEF DESCRIPTION OF THE DRAWINGS

The present technology is described in conjunction with the appendedfigures:

FIGS. 1 and 2 illustrate systems that may be used to produce prepregsthat are fully impregnated with a thermoplastic polymer.

FIG. 3 illustrates a molecular structure of cyclic butyleneterephthalate (CBT).

FIG. 4 illustrates a method of forming a fully impregnated thermoplasticprepreg product.

FIG. 5 illustrates another method of forming a fully impregnatedthermoplastic prepreg product.

In the appended figures, similar components and/or features may have thesame numerical reference label. Further, various components of the sametype may be distinguished by following the reference label by a letterthat distinguishes among the similar components and/or features. If onlythe first numerical reference label is used in the specification, thedescription is applicable to any one of the similar components and/orfeatures having the same first numerical reference label irrespective ofthe letter suffix.

DETAILED DESCRIPTION

The embodiments described herein relate to fully impregnatedthermoplastic prepreg products, and specifically systems and methods formaking the same. The prepreg products are fully impregnated withthermoplastic materials that allow the prepreg products to be reheatedand molded into a given shape. The prepreg products are made usingreactive resin materials, specifically monomers and oligomers. Variousreactive resins that may be utilized to form the fully impregnatedthermoplastic prepreg products are described below.

In order to achieve a commercially viable prepreg product using monomeror oligomer materials (hereinafter resins or reactive resins), theconversion of the reactive resin to a polymer needs to be greater than90% and more commonly greater than 95%. Higher molecular weights of thethermoplastic polymers are also typically desired.

The systems and methods described herein are useful for manufacturingprepreg products using reactive resins. The resin conversion rate thatis achieved via the systems and methods described herein is greater than90% and more commonly greater than 95%. In most embodiments, theconversion rate of the resins is greater than 98% or even greater than99%. In addition, the systems and methods described herein are able toachieve this high conversion rate utilizing a continuous process,wherein a fabric or mat material (woven or nonwoven) is essentiallymoved constantly or continually throughout the manufacturing process.The continuous process greatly increases the efficiency of themanufacturing process, which decreases the overall cost of the finalprepreg product. For example, the manufacturing time between coating ofthe reactive resin (e.g., MMA, CBT, and the like) to the formation of afully impregnated thermoplastic prepreg may be less than 20 minutes andcommonly less than 10 minutes. In many embodiments, this processing timemay be less than 5 minutes.

The systems and methods described herein are also able to achieve fulland complete impregnation of the reinforcing fibers with thethermoplastic polymer. The low viscosity of the reactive resin materialallows the resin to easily penetrate within and saturate the fabric ormat. The low viscosity of the reactive resin allows the resin to flowwithin and fully saturate either a single layer of the fabric or mat, ormultiple layers of these materials. Accordingly, the systems and methodsdescribed herein are capable of producing prepregs that include multiplelayers of materials with each layer being fully saturated or impregnatedwith the thermoplastic polymer materials. The final prepreg product canbe made flexible with high content of reinforcing fibers. The prepregsmay be rolled into a rolled product.

The embodiments described herein provide a process and apparatus thatutilizes mixing of reactive resin components, followed by application ofthe reactive resin components to a fibrous media. The reactive resincomponents are then cured in an oven to form a fully impregnatedthermoplastic prepreg having a thermoplastic polymer matrix. The systemsdescribed herein may be modified to accommodate the specificrequirements of each reactive resin described herein, which enablepolymerization of the reactive resins.

The term roving as used herein refers to a bundle of fibers that arepositioned adjacent one another to form a rope, thread, or cord likecomponent. A common type of fiber that is used in the rovings is glassfibers, although various other fibers could be used such as carbonfibers, basalt fibers, metal fibers, ceramic fiber, natural fibers,synthetic organic fibers such as aramid fibers, and other inorganicfibers. The term fabric or mat as used herein refers to woven ornonwoven materials. The woven materials are materials that are producedby weaving multiple roving strands together. The roving strands arecommonly woven so that a first plurality of strands extend in a firstdirection (e.g., weft direction) and a second plurality of strandsextend in a second direction that is typically orthogonal to the firstdirection (e.g., warp direction). The first plurality of strands areroughly parallel with one another as are the second plurality ofstrands. The woven fabrics or cloths may be unidirectional, where all ormost of the roving strands run or extend in the same direction, or maybe bidirectional, wherein the roving strands run in two, typicallyorthogonal, directions. Various weaves may be used to form the fabric ormats described herein, including: plain weaves, twill weaves, satinweaves, multiaxial weaves, or stitching. The woven cloths or fabricsthat are employed may contain any kind of woven fabric or multi-axialfiber material. The fabrics or mats may also contain chopped fibers inaddition to or alternatively from the continuous fibers. The fabrics ormats may be a hybrid from different type of fibers. For ease indescribing the embodiments herein, the embodiments will generally referto the use of glass fibers, although it should be realized that variousother fiber types may be used.

As briefly described above, nonwoven fiber mats are used in addition toor in place of the woven reinforcement fabrics. The nonwoven fiber matsare commonly formed of fibers that are entangled, needled, or meshedtogether rather than being woven in a uniform direction. The nonwovenfiber mats exhibit more uniform strength characteristics in comparisonto the woven reinforcement fabrics. Stated differently, the strength ofthe nonwoven fiber mats is typically less directionally dependent sothat a more uniform strength is achieved regardless of which directionthe mat is tensioned. In comparison, the strength of the wovenreinforcement fabrics are directionally dependent whereby the fabrics orcloths exhibit substantially more strength in a direction aligned withthe fibers and less strength in a direction misaligned from the fibers.The reinforcement fabrics or cloths are substantially stronger than thenonwoven mats when the tension is aligned with the fibers. For ease indescribing the embodiments herein, the embodiments will generally referto fabrics or mats, which is intended to apply to both woven fabrics orcloths and nonwoven fiber mats.

The fibers used in the fabrics or mats may be treated with a sizingcomposition including coupling agent(s) that promote bonding betweenreinforcing fibers and polymer resin. For example, the fibers may besized with one or more coupling agents that covalently bond thethermoplastic resin to the fibers. Exemplary coupling agents may includecoupling agents having a silicon-containing moiety and a reactiveacrylate or methacrylate moiety that may copolymerize with methylmethacrylate monomers during polymerization. Specific examples ofcoupling agents include (methacryloxypropyl)trimethoxysilane and(acryloxypropyl)trimethoxysilane.

The term thermoplastic polymer or material refers to polymers that arecapable of being melted and molded or formed into various shapesmultiple times. As such, the fully impregnated thermoplastic prepregsmay be positioned in a mold and reformed or remolded into variousdesired shapes. Examples of polymer materials or resins that may be usedwith the embodiments herein include polymethacrylates, polyesters, andthermoplastic polyurethanes.

The description and/or claims herein may use relative terms indescribing features or aspects of the embodiments. For example, thedescription and/or claims may use terms such as relatively, about,substantially, between, approximately, and the like. These relativeterms are meant to account for deviations that may result in practicingand/or producing the embodiments described herein. For example, theclaims and/or description may describe the fabric or mat beingcontinuously moved through the process. A skilled artisan wouldrecognize that some negligible stoppage or non-movement of the fabric ormat may occur without departing from the spirit of the disclosureherein. These deviations of differences may be up to about 10%, but aretypically less than 5%, or even 1%. A similar rationale applies to anyof the other relative terms used herein.

In producing conventional thermoplastic prepregs, the process of fullyimpregnating or saturating the fabric or mat is rather expensive and/ordifficult due to the high melt viscosity of the thermoplastic polymerresin. In some instances, a solvent is added to the polymerresin/thermoplastic material to reduce the viscosity of the material.While the reduced viscosity may aid in fully impregnating thereinforcement fabric, the solvent needs to be subsequently removed fromthe fabric after the polymer resin/thermoplastic material is impregnatedwithin the fabric. Removal of the solvent commonly involves heating thefabric to evaporate the solvent, adding cost and environmental concerns.

Other conventional technologies use pre-impregnated thermoplastic tapesof polymer resin and reinforcing fibers. These tapes are typicallymanufactured as a single layer by applying a molten polymer resin atopflattened rovings. For example, glass rovings may be passed over rollersto flatten and spread fibers that are then coated with a molten polymerresin. The tapes are then cooled with the glass fibers encased withinthe hardened polymer resin material. The tapes may then be used inproducing other products, typically by stacking and consolidatingseveral layers of tape together. The process of spreading fibers forresin impregnation typically limits to rovings; since spreading fibersin fabrics or mats is nearly impossible. In addition, the stacked tapeis often rigid due to the polymer resin that impregnates the tapelayers, which makes it difficult to mold intricate shapes.

In contrast to conventional prepregs, the production of thethermoplastic prepregs described herein is fast and simple. For example,fully saturating the fabric or mat is relatively easy since the reactiveresin materials (e.g., MMA, CBT, and the like) have a low viscosity thatis lower than 10.0 poises, more typically lower than 1.0 poise. This lowviscosity allows the resin materials to easily flow within and fullysaturate a single or multiple layers of the fabric or mat. The capillaryforce of the rovings or fibers further aids in saturating the fabric ormat with reactive resins. The low viscosity of these materials alsoallows the materials to be applied to a constantly or continually movingsheet of material. The resins may then be converted into a thermoplasticpolymer material so that the resulting fabric or mat is fullyimpregnated with the thermoplastic resin.

While the embodiment herein generally refers to the manufacture ofpolymethyl methacrylate prepregs, other reactive resin systems can beeasily adapted to work with the same or similar apparatus to formthermoplastic prepregs including polyesters and thermoplasticpolyurethanes, and blends of thermoplastic polymers.

Having described several aspects of the embodiments generally,additional aspects will be evident with reference to the description ofthe several drawings provided below.

Systems

Referring now to FIGS. 1 and 2, illustrated is a system that may be usedto produce prepregs that are fully impregnated with any of thethermoplastic polymers described below. The various monomers oroligomers that may polymerize to form thermoplastic polymers willgenerally be referred to hereinafter as reactive resins. FIGS. 1 and 2illustrate a general configuration of the system that may be used. Anyspecific modifications of the system and/or components that may be addedor removed from the system are described in greater detail in thespecific sections below describing the various reactive resins.

The systems of FIGS. 1 and 2 are capable of producing the fullyimpregnated thermoplastic prepregs in a continuous process, wherein afabric or mat 4 is continually or constantly in movement through thesystem. Stated differently, the term continuous process means that theprocess is not interrupted or paused in performing any one process step.Rather, each step in the process is continually or constantly beingperformed. For example, the fabric or mat is continually moved from arolled good, coated with the reactive resin material, cured in the oven,and rolled into a final product. In contrast, conventional systemstypically are halted or interrupted during the performance of one ormore steps, such as the impregnation of fibrous substrates with highmelt viscosity thermoplastic polymer resin.

In some embodiments, the system includes two vessels or holding tanks(i.e., 1 and 2). The holding tanks, 1 and 2, may be heated. One of theholding tanks (e.g., holding tank 1) may contain the reactive resin. Theother holding tank (e.g., tank 2) may contain an initiator and/orcatalyst as specifically described below for each reactive resin. Theholding tanks, 1 and 2, may be heated to a temperature that aids informing the application and/or polymerization process. Specific detailson the contents of the holding tanks and/or any heating are described ingreater detail below. In some embodiments the system may include asingle holding tank, which may include only the reactive resin or acombination of the reactive resin and an initiator and/or catalyst.

The reactants from the two holding tanks, 1 and 2, may be metered into astatic mixer or mixing head 3 that ensures the correct ratio of thereactive resin and any initiator and/or catalyst. The components fromthe two holding tanks, 1 and 2, are thoroughly mixed in the static mixer3 into a substantially homogenous mixture. In some embodiments thestatic mixer 3 may not be used, such as when a single holding tank(e.g., tank 1) is employed.

A fabric or mat 4 is unwound or otherwise provided to the system. Thesystem may include a mechanism that unwinds the fabric or mat and movesthe fabric or mat through the system and along or about the variousprocesses. In some embodiments, the mechanism may include poweredrollers or calendars, a conveyor system, or a double belt compressionoven, that move the fabric or mat 4 through the system.

In some embodiments, the initiator and/or catalyst (hereinafterpolymerization component) may be included on the surface of the fibers.When the fabric or mat 4 includes the polymerization component, only asingle holding tank (e.g., tank 1) containing the reactive resin may beused, or a reduce amount of the polymerization component may becontained in the second holding tank (e.g., tank 2) and/or mixed withthe reactive resin in the single holding tank (e.g., tank 1). In someembodiments, two holding tanks, 1 and 2, may be used and each holdingtank may include a different reactive resin material described below.For example, a first holding tank 1 may include methyl methacrylate(MMA) monomers while the second holding tank 2 includes cyclic butyleneterephthalate (CBT). In such instances, a combination of two or moretypes of reactive resins may be applied to the fabric or mat.

The fibers of the fabric or mat 4 may also be treated with a sizingcomponent, such as a mixture of silane coupling agents, polymeric filmformers, and other additives that are designed to enhance theinterfacial bonding between the glass fiber and the reactive resin. Forexample, a reactive silane may have a polymerizable moiety thatcopolymerizes with monomers or oligomers, thus improving the couplingbetween the reinforcing fibers and the thermoplastic resin matrix toimprove composite properties.

In some embodiments, after the fabric or mat 4 is unwound, or during theunrolling of the fabric or mat, the fabric or mat may be subjected to apreheating operation. The preheating operation may be performed to heatthe fabric or mat 4, such as to aid in polymerization of the reactiveresin and/or to remove residual moisture from one or more surfaces ofthe fabric or mat. As illustrated in FIG. 1, an infrared heater 5 may beused to raise the temperature of the fabric or mat 4 prior to coatingthe reactive resin on the fabric or mat. The preheating of the fabric ormat 4, and/or the preheating of the reactive resin, may be employed toprevent the reactive resin from solidifying upon contact with the fibersof the fabric or mat 4, which may ensure a good wet out of the resin athigher line speeds. In a specific embodiment, the infrared heater 5 maybe positioned atop or over the fabric or mat 4 to heat the fabric ormat. In some embodiments, a second heater (not shown) can be positionedon an opposite side (e.g., bottom side) of the fabric or mat 4 tofurther aid in preheating the fabric or mat. In other embodiments, apreheating oven may be used in place of or in addition to the infraredheater 5. In some embodiments, the temperature of the preheatingmechanism may be greater than a polymerization temperature of thereactive resin. As shown in FIG. 2, in some embodiments the system maynot include a preheating system or assembly, such as the infrared heater5. Such embodiments may be especially useful when the reactive resin ishighly sensitive or dependent on temperature.

The reactive resin is then applied to the fabric or mat 4 using a slotdie 6 or other resin application mechanism. The slot die 6 may bepositioned atop or adjacent one or more surfaces of the fabric or mat 4.In some embodiments, the resin mixture is typically applied as close aspossible to an inlet of the curing oven 8. This may be done to minimizeexposure of the reactive resin to the surrounding air, to minimizeevaporative vapors of the reactive resin, to minimize temperatureincreases or decreases of the reactive resin from the surroundingenvironment, and the like. The slot die 6 may be positioned directlyadjacent to the inlet of the curing oven 8. In some embodiments, theslot of the slot die 6 may have an opening of about 1.0 mm or less thatenables the use of a very thin die. The thin die allows the distal endof the die to be positioned substantially close to the curing oven 8 tominimize the exposure of the resin mixture to the surroundingenvironment. In some embodiment, the distal end of the slot die 6 may bepositioned within 1.0 inches of the curing oven's inlet, and preferablywithin 0.5 inches of the inlet. The slot die 6 may be temperaturecontrolled in order to achieve a temperature range as specified in thedescription of the respective reactive resins. The slot die 6 mayinclude a thermocouple and heating cartridge or other heating componentto ensure that the slot die 6 remains within the desired temperaturerange.

While the embodiment herein utilizes a slot die 6 for application of theresin mixture to the fabric or mat 4, the low viscosity of such systemsallows a wide range of application technologies including, but notlimited to, spray application, curtain coating, dip and squeeze coating,kiss roll application, doctor blade application, or even powder coatingof pre-ground solid resins where the curing oven can also be utilized tomelt the reactive components.

The system may include a hood or enclosure 7 that is fully covers orencloses at least a portion of the fabric or mat 4. In some embodiments,the hood or enclosure 7 may be integrally formed with the oven 8, suchas by forming or defining a proximal front end of the oven 8. In otherembodiments, the hood or enclosure 7 may be a separate component that isattached to the front of the oven 8. For example, the hood or enclosure7 may be a separate component that is removably coupleable with aproximal front end of the oven 8. In either instance, the hood orenclosure 7 may be configured to fully cover and enclose the die 6. Insuch embodiments, the reactive resin may be applied to the fabric or mat4 without being exposed to the surrounding environment, or with minimalexposure to the surrounding environment. Stated differently, thereactive resin may be applied to the fabric or mat 4 while being fullyenclosed or covered by the hood or enclosure 7 and/or curing oven.

The hood or enclosure 7 may include ports, apertures, other featuresthat allow the fluid lines of the die 6 to be positioned through a frontsurface of the hood or enclosure 7. One or more exhaust components 10may be fluidly coupled with the hood or enclosure 7 and may beconfigured to remove exhaust gases and/or other gases from the hood orenclosure 7. The exhaust component may include various fluid lines,ports, pumps, valves, purge valves, or other components. Exhausting thegases may be important when vapors from the reactive resin and/or anyother materials are present within the hood or enclosure 7. Exhaustingthese gases may also reduce or eliminate exposure of these substances toworkers or other individuals. In some embodiments, a fluid inletcomponent (not shown) may also be attached to the hood or enclosure 7.The fluid inlet component may include various fluid lines, ports, pumps,valves, and the like, and may be used to introduce various gases orsubstances that may aid in polymerization of the reactive resin and/orcontrol/maintain a desired environment within the hood or enclosure 7.

The liquid handling lines between the tank(s), 1 and/or 2, and thestatic mixer 3 and/or between the mixer 3 and the slot die 6 may beinsulated to minimize heat loss as the reactive resin and/orpolymerization component flows through the handling lines. In someembodiments, the liquid handling lines are heated in addition to beinginsulated to ensure that the liquid materials (e.g., reactive resinsand/or polymerization component) are maintained within a constanttemperature range. The temperature may be maintained within the rangesdescribed below for the various reasons described herein, such as toprevent solidification of the reactive resins, to control viscosity, andthe like. The system may also be configured to recirculate the liquidmaterials as desired, such as to prevent or minimize material build upin the system and/or liquid handling lines.

After the fabric or mat 4 is coated and/or saturated with the reactiveresin, the reactive resin impregnated fabric or mat 4 is then passedthrough a curing oven 8. The temperature of the curing oven 8 ismaintained at the temperatures described below to ensure the completionof the polymerization of the reactive resin to a thermoplastic polymer.Stated differently, the curing oven 8 is maintained above apolymerization temperature at which the monomers and/or oligomers startto polymerize. The coated fabric or mat 4 may be exposed to the curingoven 8 for a time which is sufficient to ensure complete polymerizationof the reactive resin material. When the reactive resin composition is acombination of two or more types of reactive monomers and/or oligomersdescribed below, the heating temperature of the resin-fiber mixture maybe chosen to be above the threshold polymerization temperatures of allthe reactive resins. Alternatively, the heating temperature of theresin-fiber mixture may be chosen to be above a threshold polymerizationtemperature of one type of monomer/oligomer but below a thresholdpolymerization temperature of the other type of monomer/oligomer.

In some embodiments, the coated fabric or mat 4 is subjected to a pressmechanism that facilitates in complete wet-out of the reinforcing fibersby the reactive resin. In one embodiment, the press mechanism mayinclude one or more calendars that press or squeeze the reactive resinthrough the fabric or mat 4. In another embodiment, the curing oven 8may be a double belt compression oven where the pressure on the belts isadjustable to facilitate complete wet-out of the reinforcing fibers bythe reactive resin.

Upon exiting the curing oven 8, the fully impregnated thermoplasticprepreg 9 may be collected. In some embodiments, the system includes awinding mechanism that is configured to wind the fully impregnatedthermoplastic prepreg 9, which is relatively flexible in comparison withconventional prepregs, due to the high content of reinforcing fibersthat can be achieved with the process in the instant invention. In otherembodiments, the fully impregnated thermoplastic prepreg may be cut intosheets, which may be stacked atop one another.

The systems of FIGS. 1 and 2 are designed so that the above process isable to be performed in a time of 20 minutes or less, and more commonly10 minutes or less. In some embodiments, the process may be performed in5 minutes or less. Specifically, the time period between when the fabricor mat 4 is initially unwound to when the fully impregnatedthermoplastic prepreg exits the curing oven 8 may be 20 minutes or less,10 minutes or less, or in some embodiments 5 minutes or less. This speedand impregnation efficiency is not achievable via conventional systemsusing polymer resin materials. Moreover, the speed and efficiency is notdrastically affected when multiple stacked layers of the fabric or mat 4are employed. Rather, the low viscosity of the reactive resins describedbelow are able to easily penetrate through and saturate the multiplestacked layers of fabric or mat 4 so that the processing time of thestacked layers of the fabric or mat remains low. Full impregnation ofthe stacked layers of the fabric or mat 4 is achievable due to the lowviscosity of the reactive resin materials.

Exemplary Reactive Resins

Described below are various reactive resins that may be utilized oremployed in forming the fully impregnated thermoplastic prepregsdescribed herein. The reactive resins may be used in isolation to formthe prepreg, or in some embodiments may be used in combination to formthe prepregs. The systems illustrated in FIGS. 1 and 2 and describedabove may be used with each of the reactive resins described below toform the fully impregnated thermoplastic prepregs. Specificmodifications to the above systems that may be required when using thespecific reactive resins will be described in the respective section foreach resin.

Polymethyl Methacrylate (PMMA)

In some embodiments, methyl methacrylate (MMA) monomers may be appliedto the fabric or mat and subsequently reacted to form polymethylmethacrylate (PMMA). The (MMA) monomers are liquid at room temperaturesand have a very low viscosity (e.g., lower than 1.0 poise). Free radicalpolymerization of the MMA monomer into its polymer PMMA is usuallyconducted at temperature between 40° C.-100° C. using an initiator, suchas an organic peroxide. An exemplary organic peroxide is a low viscosityaqueous benzoyl peroxide, such as Luperox® EZ-FLO that is commerciallyavailable from Arkema S.A. In some embodiments, the MMA monomer alone orin isolation may be added to the fabric or mat. Stated differently, thematerial that is applied to the fabric or mat via tanks 1 and/or 2 mayinclude greater than 90% MMA monomer, greater than 95% MMA monomer, oreven greater than 98 or 99% MMA monomer. In such embodiments, a singletank (i.e., either tank 1 or 2) may be used in the above describedsystem.

During polymerization of the MMA monomer, the density of the resintypically increases from about 0.9 g/cm³ to 1.2 g/cm³ and the matrixresin typically experiences shrinkage. As such, in some embodiments apolymer material may be added to the MMA resin in order to reduceshrinkage. The polymer material may be polymethyl methacrylate (PMMA).The PMMA may dissolve in the MMA to form a homogenous liquid. The PMMAto MMA material ratio may be controlled to decrease shrinkage uponpolymerization and without substantially increasing the viscosity orotherwise maintaining a low viscosity, for example below 10 poises.

In conventional infusion processes, shrinkage of the reactive resinmaterial may alter the alignment of the fibers in the fabric or matand/or cause other changes, which may affect the structural integrity ofthe final product. In the instant invention, reinforcing fibers in thefabric or mat are under tension during the manufacturing of prepreg,therefore fiber shifting is minimized. On the other hand, one advantageof the PMMA impregnated prepreg that results from the systems describedherein is that no additional shrinkage, or a negligible amount ofadditional shrinkage, occurs during post processing of the prepreg.Stated differently, all or most of the shrinkage that may occur duringpolymerization of the reactive resin occurs during the formation of thefully impregnated thermoplastic prepreg and not during subsequentthermoforming, thermomolding, or other processing, such as in theformation of the final product as described herein.

As described briefly above, MMA monomers are sensitive to heat. Forexample, MMA typically boils at around 101° C. Evaporation of the MMAresin may also be relatively high due to the relatively low boilingpoint of the material. Because of the relatively low boiling point, itis important to ensure that any applied heat is maintained within acontrolled range below about 100° C. The polymerization rate of MMAmaterial is also highly dependent on temperature. For example, atemperature that is lower than 40° C. may result in an incompletepolymerization of the MMA material and/or substantially increases thepolymerization time. On the other hand, a temperature that is too highresults in a substantial evaporation of the MMA resin. To ensure thatthe MMA resin is fully polymerized in a short amount of time whileminimizing evaporation of the resin, the temperature of the oven 8 maybe maintained within a temperature range of between 40° C. and 100° C.,and more commonly between 60° C. and 80° C.

Because of the MMA resin's sensitivity to heat, it may be preferable touse the oven configuration of FIG. 2 that does not include a pre-heatingassembly 5. The oven configuration of FIG. 2 may minimize evaporation ofthe MMA resin by ensuring that the resin is not overly heated prior toentering the oven 8. In such embodiments, the MMA resin may bepre-heated in the tank (i.e., tank 1 and/or 2) to bring the MMA resin toa desired temperature before it is applied to the fabric or mat. Forexample, the MMA resin may be pre-heated above 40° C. and below 80° C.(e.g., to around 60° C.) in the tank and then applied to the fabric ormat. Pre-heating the MMA resin may aid in quickly polymerizing the MMAresin after it is applied to the fabric or mat 4 by reducing thetemperature difference between the MMA resin and the oven 8. Maintainingthe MMA resin at above 40° C. and below 80° C., and preferably at around60° C., also minimizes evaporation of the MMA resin. In otherembodiments, the oven configuration of FIG. 1 may be used, but thepre-heating assembly 5 may be tightly controlled to ensure that thetemperature of the fabric or mat remains below a certain temperature,such as 100° C. or 80° C.

To further reduce or eliminate evaporation issues, the die 6 may bepositioned close to the entrance of the oven 8. For example, the die 6may be positioned within 6 inches of the oven's entrance, or morepreferably within 4 inches or 2 inches. The die 6 may have a narrowapplication end as described herein to enable the end of the die 6 to bepositioned extremely close to the oven's entrance. In anotherembodiment, the die 6 may be positioned within the hood or enclosure 7so that the fabric or mat passes into the hood or enclosure 7 before theMMA resin is applied. The hood or enclosure 7 may be integrally formedwith the oven 8, or may be a separate component that is attached to thefront of the oven 8 to cover the die 6. For example, the hood orenclosure 7 may be a separate component that is removably coupleablewith the oven 8. In such embodiments, the hood or enclosure 7 mayinclude ports, apertures, and other features that allow the fluid linesof the die to be positioned through a front surface of the hood orenclosure 7. Any MMA resin vapors due to evaporation of the material maybe removed from the hood or enclosure 7 via exhaust line 10 that isfluidly coupled with the hood or enclosure 7 and/or the oven 8. The hoodor enclosure 7 may be not be heated or may form a portion of the oven 8that is not heated so as to prevent or minimize evaporation of the MMAresin.

In some embodiments, the oven 8 is a double belt press oven having apair of belts that are positioned on opposing surfaces of the fabric ormat so that the fabric or mat is sandwiched between the belts. The pairof belts may apply pressure to the sandwiched fabric or mat, which mayaid in spreading the MMA resin throughout the fabric or mat. In someembodiments, the sizings of reinforcing fibers (e.g., glass fibers) ofthe fabric or mat could be tailored to have a functional group thatcovalently bonds with the PMMA resin, which may result in a better bondbetween the fibers and PMMA resin. For example, the glass fiber sizingsmay contain acrylate or methacrylate functional silanes. Acrylate ormethacrylate functionality of the silane coupling agents cancopolymerize with MMA, thereby improving bonding between the PMMA resinmatrix and the reinforcing fibers.

Unlike other reactive resins, the MMA resin is not sensitive tomoisture. As such, the oven system or configuration does not need toinclude components that minimize moisture, such as a moisture free gasapplication component and/or moisture free hood or enclosure. The fabricor mat 4 also does not need to be pre-heated as in other ovenconfigurations or systems. The MMA resin is highly reactive and thus,the polymerization need only be started or initiated with heating fromthe oven 8 or another component prior to the oven (e.g., pre-heatingassembly 5). In such embodiments, the oven 8 temperature may becontrolled to manage the resulting exothermic polymerization of the MMAresin.

As briefly mentioned above, the resin application system may include asingle tank or multiple tanks. When a single tank is used (e.g., tank 1of FIG. 1 or 2), the MMA resin and/or a pre-polymer (i.e., a mixture ofthe MMA monomer and PMMA polymer) may be contained in the single tank.In some embodiments, the initiator may also be included with the MMAresin and/or pre-polymer in the single tank. In such embodiments, theliquid solution in the single tank is maintained at a low temperature(i.e., below 30° C.) to minimize premature polymerization of thematerial. In other embodiments, the initiator may be pre-applied to thefabric or mat 4 and not included within the MMA resin and/or pre-polymerin the single tank, or may be included at very low levels. In suchembodiments, the temperature of the liquid solution may be higher sincepremature polymerization is of less concern.

When multiple tanks are used (e.g., tanks 1 and 2 of FIG. 1 or 2), oneof the tanks (e.g., tank 1) may include the MMA resin monomer and/orpre-polymer solution while the other tank (e.g., tank 2) includes theinitiator. The initiator and MMA resin/pre-polymer may be mixed viamixer 3. The temperatures of the two tanks, 1 and 2, may be maintainedat a temperature of between 40° C. and 80° C., and more commonly 60° C.,since premature polymerization is not of concern.

Polyesters

In some embodiments, macrocyclic polyester oligomers may be applied tothe fabric or mat 4 and subsequently reacted to form a polyesterprepreg. The macrocyclic polyester oligomers, such as cyclic butyleneterephthalate (CBT) and cyclic ethylene terephthalate (CET), can bepolymerized to form polyesters such as polybutylene terephthalate (PBT)and polyethylene terephthalate (PET) through ring-openingpolymerization. Cyclic butylene terephthalate (CBT) is a mixture ofcyclic oligomers of butylene terephthalate. FIG. 3 illustrates themolecular structure of CBT.

CBT oligomers can be polymerized into PBT using a variety of catalysts.Suitable catalysts include organo-tin and/or organo-titanate compounds.Exemplary organo-tin catalysts include monoalkyl tin(IV) hydroxideoxides, monoalkyl tin(IV) chloride dihydroxides, dialkyl tin(IV) oxides,bistrialkyl tin(IV) oxides, monoalkyl tin(V) tris-alkoxides, dialkyltin(IV) dialkoxides, and trialkyl tin(IV) alkoxides, among othertin-containing compounds. Exemplary organo-titanate catalysts includetitanate tetraalkoxide compounds and tetraalkyl titanate compounds(e.g., tetra(2-ethylhexyl) titanate), among others.

Macrocyclic polyester oligomers, such as CBT, are solid at roomtemperature and therefore the tank that contains the macrocyclicpolyester oligomers (e.g., tank 1 or 2) and the fluid lines thattransport the macrocyclic polyester oligomers are typically heated andinsulated at above the melting point of the polyester oligomermaterials. In many instance, the polymerization temperature of themacrocyclic polyester oligomers is slightly higher than the meltingtemperature. As such, there is typically a tight temperature range orwindow for processing CBT resins.

For example, the melting point of CBT is approximately 160° Celsius(e.g., between 150° C.-190° C.) while the polymerization temperature ofCBT typically occurs at a temperature greater than 180° C. (e.g.,between 180° C.-220° C.). As such, the difference in the meltingtemperature and the polymerization temperature is roughly about 20° C.on average. Due to the close proximity between CBT's melting temperatureand polymerization temperature, the macrocyclic polyester oligomer andthe catalyst should not be mixed in tank (e.g., tank 1 or 2), in orderto prevent premature polymerization.

In other embodiments, premature polymerization or undesired mixing ofthe catalyst and macrocyclic polyester oligomer may be prevented byapplying the catalyst to the reinforcing fibers of the fabric or mat 4.The catalyst may be applied to the reinforcing fibers as part of asizing package. Exemplary methods of applying the catalyst to thereinforcing fibers is described in U.S. patent application Ser. No.12/913,326, filed Oct. 27, 2010, entitled “Fibers Treated WithPolymerization Compounds and Fiber Reinforced Composites MadeTherefrom”, the entire disclosure of which is incorporated by referenceherein.

In yet other embodiments, the system may include two tanks (e.g., tanks1 and 2) where the macrocyclic polyester oligomer is contained in onetank (e.g., tank 1) and the catalyst is contained in the other tank(e.g., tank 2). In such embodiments, the macrocyclic polyester oligomerand catalyst may be mixed at the mixer 3, prior to the application ofthe reactive resin mixture to the fabric or mat 4.

Upon application of the mixture of the macrocyclic polyester oligomerand catalyst to the fabric or mat 4, the coated fabric or mat isimmediately fed into the oven 8. In some embodiments, the fabric or mat4 may be pre-heated via pre-heating assembly. Pre-heating of the fabricor mat 4 may ensure that the macrocyclic polyester oligomer does notsolidify upon, or subsequent to, application to the fabric or mat 4. Forexample, because the macrocyclic polyester oligomer is maintained atclose to its melting temperature (e.g., 160° C.) in the holding tankand/or fluid lines, application of the macrocyclic polyester oligomer toan ambient temperature fabric or mat 4 may cause the macrocyclicpolyester oligomer to begin to solidify. To counter this possibleeffect, one or more surfaces of the fabric or mat 4, or the entirefabric or mat, may be pre-heated to near or above the meltingtemperature of the macrocyclic polyester oligomer. In some embodiments,one or more surfaces of the fabric or mat 4, or the entire fabric ormat, may be pre-heated to between 100° C. and 200° C., more commonlybetween 140° C. and 180° C., and most commonly between 160° C. and 180°C.

In some embodiments, one or more surfaces of the fabric or mat 4, or theentire fabric or mat, may be pre-heated above the polymerizationtemperature of the macrocyclic polyester oligomer. For example, one ormore surfaces of the fabric or mat 4, or the entire fabric or mat, maybe pre-heated to a temperature greater than 180° C., greater than 200°C., or even greater than 220° C. These temperatures of the fabric or mat4 may be sufficient to cause or begin polymerization of the macrocyclicpolyester oligomer upon application of the macrocyclic polyesteroligomer and prior to the fabric or mat entering the oven 8. Suchpolymerization of the macrocyclic polyester oligomer is typically not aconcern, however, since the fabric or mat 4 is commonly directedimmediately into the oven 8 where full polymerization of the macrocyclicpolyester oligomer is achieved.

Thermoplastic Polyurethanes

In some embodiments, components of thermoplastic polyurethane materials(TPU) may be applied to the fabric or mat 4 and subsequently reacted toform a TPU prepreg. TPUs are synthesized by the reaction of pre-polymerspossessing isocyanate (NCO) end groups with curatives. Typically, apre-polymer is synthesized by reacting a long chain polyol withdiisocyanates to form a molecule with reactive isocyanate groups on bothchain ends. Depending on the requirements of the end application, longchain polyols of the polyether type and polyester type may be used tomake pre-polymers.

The pre-polymers can be cured with a wide variety of curatives to formTPUs. The choice of curatives depends on the required physical andchemical properties as well as the processing and curing conditions.Typical curatives for TPUs are difunctional, such as diamines, diols,and hydroxy amines. The reaction between the pre-polymer and thecurative forms urethane links (in the case of diol curative) or urealinks (in the case of diamine curative).

Isocyanate functionalities in the pre-polymers are very reactive, andwill react readily with hydroxyl or amino groups on curative molecules.Therefore the mixture of pre-polymer and curative has a limited life. Inconventional processes that involve casting of thermoplasticpolyurethane, it is often required that the pre-polymer-curative mixturebe prepared right before they are used for casting. The limited life ofthe pre-polymer-curative mixture limits the processing window ofcomposite manufacturing processes. In the system described herein, thetwo tanks (e.g., tanks 1 and 2) allow the reactants to be separated. Thetwo reactants may be mixed (e.g., via static mixer 3) immediately priorto application of the material to the fabric or mat 4, therebyeliminating limited life issues associated with conventionalpre-polymer-curative mixtures. In such embodiments, one of the tanks(e.g., tank 1) may include the pre-polymer (e.g., with isocyanatefunctional groups at both chain ends) while the other tank (e.g., tank2) includes the curative.

Alternatively, the system may employ a single tank. In such embodiments,the pre-polymer may be contained in the single tank (e.g., tank 1). Thecurative may be applied onto the reinforcing fibers as part of a sizingpackage so that the two components are mixed upon application of thepre-polymer to the fabric or mat 4. In some embodiments, part or theentire curative can be applied onto reinforcing fibers as a sizingingredient. Applying the curative onto the reinforcing fibers may enablethe reduction of curative in a separate tank (e.g., tank 2) orcompletely eliminate the tank for the curative.

In some embodiments, it may be desirable to reduce the moisture contentof the fabric or mat 4. In such embodiments, the fabric or mat 4 may bepre-dried via pre-heating assembly 5.

Polycarbonates

In some embodiments, reactive components of polycarbonates may beapplied to the fabric or mat 4 to form a fully impregnated thermoplasticprepreg. Specifically, macrocyclic Bisphenol-A oligomers can bepolymerized into polycarbonate (PC) through ring opening polymerization,using alkali metal based initiators such as sec-butyllithium, andsodium- and potassium naphthalene. The polymerization may be conductedat a temperature between 240° C. and 280° C. and may use anionicinitiators. For example, when polymerized at 250° C., high molecularweight polycarbonates can be formed within 2-5 minutes.

In some embodiments, the system includes a two tank arrangement as shownin FIGS. 1 and 2. In such embodiments, one of the tanks (e.g., tank 1)may contain the macrocyclic Bisphenol-A oligomers while the other tank(e.g., tank 2) includes the initiator. The oligomer and initiator may bemixed via static mixer 3 and applied via die 6. The fabric or mat 4 maythen be passed through the oven 8 in a continuous process as describedabove to form the PC prepreg.

Exemplary Prepregs

The above system may be used to manufacture a fully impregnatedthermoplastic prepreg. The thermoplastic prepreg may include a fabric ormat. In one embodiment, the fabric or mat may include a plurality ofrovings that are woven together. Each roving may contain a bundle ofcontinuous glass fibers or any other fibers. In another embodiment, thefabric or mat may include a plurality of entangled and intermeshedfibers that are randomly oriented. The prepreg also includes athermoplastic polymer that is fully impregnated within the fabric ormat. The thermoplastic polymer is formed by reacting one or morereactive resins described above to form the thermoplastic polymer. Thereactive resin(s) is typically mixed with a polymerization componentthat aids in the polymerization process. As described herein, greaterthan 90%, 95%, 98%, or even 99% of the reactive resin reacts to form thethermoplastic polymer. When the fully impregnated thermoplastic prepregis subjected to a subsequent heating and/or pressure process, thethermoplastic polymer melts or softens to allow the thermoplasticprepreg to be molded or formed into a composite part.

In some embodiments, the fully impregnated thermoplastic prepreg is arolled product. The thermoplastic prepreg may be subsequently formedinto a composite part. For example, one or more layers of thethermoplastic prepreg may be compression molded into a desired compositepart. Exemplary techniques for forming the prepregs into thefiber-reinforced composite articles may include compression molding of asingle prepreg layer, multiple prepreg layers, and/or pellets of prepregmaterial into the fiber-reinforced article. When the prepreg includespartially-polymerized resin, the compression molding process may includea heating step (e.g., hot pressing) to fully polymerize the resin. Heatmay also be used in the compression molding of fully-polymerizedprepregs to melt and mold the prepreg into the shape of the finalarticle.

The prepregs may also be used to in conjunction with other fibers andresin materials to make the final composite article. For example, theprepreg may be placed in selected sections of a tool or mold toreinforce the article and/or provide material in places that aredifficult to reach for thermoset and/or thermoplastic resins. Forexample, the prepregs may be applied to sharp corners and other highlystructured areas of a mold or layup used in reactive injection moldingprocesses (RIM), structural reactive injection molding processes (SRIM),resin transfer molding processes (RTM), vacuum-assisted resin transfermolding processes (VARTM), spray-up forming processes, filament windingprocesses, and long-fiber injection molding processes, among others. Theprepreg may also be used as local reinforcement or for overmoldingduring injection and compression molding processes including LFT (longfiber thermoplastic) and D-LFT (direct-long fiber thermoplastic).

Exemplary composite products that may be formed from the prepregsinclude: automotive components, wind turbine blade components, buildingand construction components, electrical components, sports and leisurecomponents, and/or other components. Exemplary automotive componentsincludes: cockpit, seats, instrument panels, side beams, bottom plate,bottom plate side beam, door trims, body panels, openings, underbody,front/rear modules, engine compartment, engine covers, battery trays,oil pans, bonnets/hoods, fenders, spoilers, and the like.

Exemplary wind turbine blade components include: spar cap, shells, rootinserts, and the like. Exemplary building and construction componentsinclude: columns, pediments, domes, panels, window profiles, ladderrails, and the like. Exemplary electrical components include: lightpoles, circuit boards, electrical junction boxes, and the like.Exemplary sports and leisure components include: golf club shafts, golftrolleys, and the like. Other components that may be formed form theprepregs include: components for mass transportation, agriculturalequipment, and trailers/RV including passenger seats, standbacks, wallcladdings, floor panels, large panels for trailer walls, truck andtractor cabs, bus body shells, cargo containers, and the like.

In a specific embodiment, a battery tray or compartment for an electriccar or vehicle may be molded using the fully impregnated thermoplasticprepregs described herein. The battery compartment may be molded from asingle piece of the prepreg material, thereby eliminating the need touse unidirectional tape on the corners or edges to reinforce these areasof the battery compartment, as is done in conventional processes.

Methods

Exemplary methods are described herein. While the methods generallyrelate to systems that are configured to apply methyl methacrylate (MMA)resins, it should be realized that the methods and/or systems may bemodified as described herein to accommodate the other reactive resins.Accordingly, the methods are not limited to the application of MMAresins.

Referring now to FIG. 4, illustrated is an embodiment of a method 400 offorming a fully impregnated polymethyl methacrylate thermoplasticprepreg. At block 410, a fabric or mat is moved from a starting point toan ending point. The fabric or mat is subjected to a plurality ofprocesses during movement of the fabric or mat between the startingpoint and ending point. The fabric or mat is also in substantiallyconstant movement between the starting point and ending point. At block420, methyl methacrylate (MMA) resin is mixed with an initiator to forman MMA resin mixture. The initiator facilitates in polymerizing the MMAresin to form polymethyl methacrylate (PMMA).

At block 430, the MMA resin mixture is applied to the fabric or mat. Atblock 440, the MMA resin mixture coated fabric or mat is passed througha calendar or press to press the MMA resin mixture entirely through thefabric or mat such that the MMA resin mixture fully saturates the fabricor mat. At block 450, the MMA resin mixture coated fabric or mat ispassed through a curing oven having a temperature that is maintained atbetween 40° C. and 100° C., and more commonly 60° C. and 80° C., topolymerize the MMA resin and thereby form PMMA. Upon exiting the curingoven, the fabric or mat is fully impregnated with PMMA. Greater than95%, 98%, or even 99% of the MMA resin may be polymerized to form PMMA.

In some embodiments, the MMA resin is mixed with the initiator in amixing component prior to application of the MMA resin to the fabric ormat. The MMA resin may include a mixture of an MMA monomer and a PMMApolymer. The MMA resin mixture may be applied to the fabric or mat via adie that is positioned within a hood or enclosure that covers andencloses at least a portion of the fabric or mat. In such embodiments,the method may also include exhausting vapors within the hood orenclosure via an exhaust component.

The curing oven may include a double belt compression oven. In suchembodiments, steps 440 and 450 (i.e., passing the fabric or mat througha press and through an oven) may occur simultaneously. The method mayfurther include winding the fully impregnated PMMA thermoplastic prepreginto a roll product.

Referring now to FIG. 5, illustrated is a method 500 of forming a fullyimpregnated polymethyl methacrylate prepreg product. At block 510, amethyl methacrylate (MMA) resin is applied to a fabric or mat. The MMAresin is combined with an initiator that facilitates in polymerizing theMMA resin to form polymethyl methacrylate (PMMA). At block 520, the MMAresin coated fabric or mat is passed through a calendar or press tofully saturate the fabric or mat with the MMA resin. At block 530, theMMA resin saturated fabric or mat is passed through a curing oven topolymerize the MMA resin throughout the fabric or mat and thereby formthe fully impregnated PMMA prepreg. The fabric or mat is constantlymoved during the above process and the above process occurs in a time ofless than 10 minutes.

In some embodiments, the method also include applying the initiator tothe fabric or mat so that the MMA resin is combined with the initiatorupon application of the MMA resin to the fabric or mat. In otherembodiments, combining the MMA resin with the initiator includes mixingthe MMA resin and the initiator prior to applying the MMA resin to thefabric or mat. The fabric or mat may include sized fibers having afunctional group that covalently bonds with the MMA resin. The MMA resinmay be or include a mixture of an MMA monomer and a PMMA polymer. Themethod may further include winding the fully impregnated thermoplasticprepreg into a roll product. The MMA resin may be applied to the fabricor mat via a die that is positioned within a hood or enclosure thatcovers and encloses at least a portion of the fabric or mat.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neither,or both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a method” includes aplurality of such methods and reference to “the glass fiber” includesreference to one or more glass fibers and equivalents thereof known tothose skilled in the art, and so forth. The invention has now beendescribed in detail for the purposes of clarity and understanding.However, it will be appreciated that certain changes and modificationsmay be practice within the scope of the appended claims.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

What is claimed is:
 1. A fiber-containing polymethyl methacrylateprepreg comprising: a first plurality of fibers; a second plurality offibers made from a different material than the first plurality offibers; and a polymerized resin comprising the polymethyl methacrylate,wherein the polymerized resin is formed from a reactive resincomposition comprising methyl methacrylate.
 2. The fiber-containingpolymethyl methacrylate prepreg of claim 1, wherein at least one of thefirst plurality of fibers and the second plurality of fibers arereactive fibers with a reactive agent present on the surface of thereactive fibers.
 3. The fiber-containing polymethyl methacrylate prepregof claim 1, wherein the first plurality of fibers and the secondplurality of fibers are formed into a fiber mat.
 4. The fiber-containingpolymethyl methacrylate prepreg of claim 1, wherein the first pluralityof fibers and the second plurality of fibers are formed into one or morelayers of fiber mat.
 5. The fiber-containing polymethyl methacrylateprepreg of claim 1, wherein the first plurality of fibers are formedinto a first fiber mat and the second plurality of fibers are formedinto a second fiber mat.
 6. The fiber-containing polymethyl methacrylateprepreg of claim 5, wherein the prepreg comprises a stack of layers ofthe first fiber mat and the second fiber mat on top of each other. 7.The fiber-containing polymethyl methacrylate prepreg of claim 1, whereinthe first plurality of fibers comprises fibers selected from glassfibers, inorganic fibers, carbon fibers, metal fibers, organic polymerfibers, and mineral fibers.
 8. The fiber-containing polymethylmethacrylate prepreg of claim 1, wherein the second plurality of fiberscomprises fibers selected from glass fibers, inorganic fibers, carbonfibers, metal fibers, organic polymer fibers, and mineral fibers.
 9. Thefiber-containing polymethyl methacrylate prepreg of claim 1, wherein thefirst plurality of fibers comprises glass fibers and the secondplurality of fibers comprises carbon fibers.
 10. The fiber-containingpolymethyl methacrylate prepreg of claim 2, wherein the reactive agentpresent on the surface of the reactive fibers comprises: a silanecoupling moiety, and a reactive acrylate or methacrylate moiety.
 11. Thefiber-containing polymethyl methacrylate prepreg of claim 1, wherein thereactive resin composition further comprises an initiator.
 12. Thefiber-containing polymethyl methacrylate prepreg of claim 12, whereinthe initiator comprises an organic peroxide.
 13. A fiber-containingpolymethyl methacrylate prepreg comprising: a stack of fiber mats incontact with a cured reactive resin composition, wherein the stack offiber mats comprise layers of a first fiber mat and a second fiber matstacked on top of each other, and wherein the first fiber mat comprisesa first plurality of fibers and the second fiber mat comprises a secondplurality of fibers made of a different material than the firstplurality of fibers, and wherein the cured reactive resin compositioncomprises a polymerized methyl methacrylate monomers.
 14. Thefiber-containing polymethyl methacrylate prepreg of claim 13, whereinthe cured reactive resin composition is formed in the prepreg bypressing and heating the stack of fiber mats to a polymerizationtemperature for the reactive resin composition.
 15. The fiber-containingpolymethyl methacrylate prepreg of claim 13, wherein the first pluralityof fibers comprises fibers selected from the group consisting of glassfibers, inorganic fibers, carbon fibers, metal fibers, organic polymerfibers, and mineral fibers.
 16. The fiber-containing polymethylmethacrylate prepreg of claim 13, wherein the second plurality of fiberscomprises fibers selected from the group consisting of glass fibers,inorganic fibers, carbon fibers, metal fibers, organic polymer fibers,and mineral fibers.
 17. The fiber-containing polymethyl methacrylateprepreg of claim 13, wherein the first plurality of fibers comprisesglass fibers and the second plurality of fibers comprises carbon fibers.18. The fiber-containing polymethyl methacrylate prepreg of claim 13,wherein at least one of the first plurality of fibers and the secondplurality of fibers are reactive fibers that have a reactive agentpresent on the surface of the fibers, wherein the reactive agentcomprises: a silane coupling moiety, and a reactive acrylate ormethacrylate moiety.
 19. The fiber-containing polymethyl methacrylateprepreg of claim 13, wherein the reactive resin composition furthercomprises an initiator.
 20. The fiber-containing polymethyl methacrylateprepreg of claim 13, wherein the initiator comprises an organicperoxide.
 21. A fiber-reinforced composite article comprising: afiber-containing polymethyl methacrylate prepreg comprising: (i) a firstplurality of fibers; (ii) a second plurality of fibers made from adifferent material than the first plurality of fibers; and (iii) apolymerized resin comprising the polymethyl methacrylate, wherein thepolymerized resin is formed from a reactive resin composition comprisingmethyl methacrylate.
 22. The fiber-reinforced composite article of claim21, wherein at least one of the first plurality of fibers and the secondplurality of fibers are reactive fibers with a reactive agent present onthe surface of the fibers.
 23. The fiber-reinforced composite article ofclaim 21, wherein the first plurality of fibers and the second pluralityof fibers are formed into a fiber mat.
 24. The fiber-reinforcedcomposite article of claim 21, wherein the first plurality of fibers andthe second plurality of fibers are formed into one or more layers offiber mat.
 25. The fiber-reinforced composite article of claim 21,wherein the first plurality of fibers are formed into a first fiber matand the second plurality of fibers are formed into a second fiber mat.26. The fiber-reinforced composite article of claim 25, wherein theprepreg comprises a stack of layers of the first fiber mat and thesecond fiber mat on top of each other.
 27. The fiber-reinforcedcomposite article of claim 21, wherein the first plurality of fiberscomprises fibers selected from glass fibers, inorganic fibers, carbonfibers, metal fibers, organic polymer fibers, and mineral fibers. 28.The fiber-reinforced composite article of claim 21, wherein the secondplurality of fibers comprises fibers selected from glass fibers,inorganic fibers, carbon fibers, metal fibers, organic polymer fibers,and mineral fibers.
 29. The fiber-reinforced composite article of claim21, wherein the first plurality of fibers comprises glass fibers and thesecond plurality of fibers comprises carbon fibers.